This invention refers to the processing of waste materials containing organic refuse, such as garbage or refuse from homes, kitchens, hotels, gardens, farms and various industrial facilities. More particularly, the invention concerns a method and apparatus for processing these waste materials by fermentation, decomposing the material into compost.
All modern industrial societies are facing increasing cost and difficulty in disposing of their enormous and increasing tonnage of solid waste and garbage in an environmentally sound and economically acceptable manner. Historically, refuse or garbage has been collected and disposed of by one of several inexpensive means, such as open burning, dumping in waterways or dumping in common landfills. As the ecological impact of these practices became evident, the demand for safer practices grew. Three methods have emerged as environmentally suitable means for safe refuse disposal: (1) sophisticated landfills with costly structures and controls designed to prevent leaching into surrounding ground water; (2) controlled incineration; and (3) composting in which the compost product has a reduced toxicity suitable for subsequent disposal in a landfill or use as fertilizer.
Microbial conversion of organic matter to compost is a natural phenomenon as old as biological matter on the planet. Composting has been used for agricultural purposes for hundreds of years. Only relatively recently has composting been used as an alternative method of handling community waste. In composting systems throughout the world, a host of classes and species of microorganisms are used to ferment a variety of organic materials. For instance, recent attention has been drawn to microorganisms adapted to decompose toxic organic materials, such as PCBs, in solid waste.
In one typical composting process, a chamber is filled with a waste material. Air is provided to the chamber to sustain the aerobic thermophilic fermentation process. The chamber is vented to prevent accumulation of CO.sub.2 generated during the fermentation, since such accumulation may halt the process or cause the fermentation to become anaerobic. It is known that the fermentation process progresses in two microbiological stages. In the first stage the fermentation is dominated by thermophilic microorganisms. The second stage is characterized by mesophilic microbial activity and gradually decreasing temperature.
In spite of the simplicity and allure of composting techniques, typical systems are not easily adapted to large scale use in smaller communities. In some cases, the systems are too costly, often as much as $75,000,000 per system. Some systems employ exposed windrows of rotting garbage, which is certainly a nuisance for the local community. Still other systems require a prohibitive amount of time to fully decompose community waste.
In order to address the growing demands of community refuse disposal, a need exists for a fermentation or composting process and apparatus to inexpensively and efficiently process the refuse.